A multiple lift mast is composed of at least one fixed mast and an extendable mast, each mast having two distanced mast profiles which are joined via cross-beams at the lower and upper ends. Two telescoping mast length portions are provided if the multiple lift masts are extendable to a large height. The length portions are moved apart by a sophisticated lifting device. This includes that the middle lift mast, at the upper end, mounts a lift chain roller which is passed over one lift chain which engages the inner mast at one end in order to extend the inner mast as well when the middle mast is being shifted. The other end of the chain is caused to rest on the fixed mast. It is known to design the mast profiles as U-profiles or even as I-profiles.
Further, it is known to guide the telescoping masts by means of suitable guide rollers in order to produce a minimal friction during extension and retraction.
A telescoping mast having the above characteristics has been known from EP 1 505 033 A1, the entire contents of which is incorporated herein by reference, for example. This state of the art has also made it known to provide the sense of rotation of lift chain rollers crosswise to the direction of travel and position the rollers between the front-end flanges of the middle and inner masts to be extended. To enable roller assembly, pockets in which the rollers run are cut into the web of the I-section profile. The effort in manufacturing them is relatively large. Moreover, this will weaken the profile geometry.
It is the object of the invention to provide a bearing assembly for lift chain rollers in a multiple lift mast for high-lift fork trucks that does not present the drawbacks mentioned and allows mounting the lift chain rollers in a simple way without weakening the mast cross-section in an unnecessary way.